Data recording method and data recording medium

ABSTRACT

The object of the present invention is to provide a data recording method and optic recording medium that is capable of reproducing address data accurately by reducing the correlation of address data between adjacent tracks, reducing the effect of cross-talk between adjacent tracks on the recording clock and by making it possible to apply a cross-talk canceller to the wobble signal. The data-recording method of recording data while controlling the correlation between a first data string and a second data string that are contained in recording data, and is provided with a selecting process of selecting inversion/no inversion of first data string such that the correlation between first data string and second data string is reduced; and a recording process of recording first data string according to selected inversion/no inversion polarity, and recording control code that indicates whether inversion/no inversion was selected for first data string.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a data recording method and datarecording medium that make it possible to suppress the effects ofcross-talk by reducing the correlation of recorded data.

[0003] 2. Description of the Related Art

[0004] Currently, optical discs, such as CDs and DVDs, are widely used.In recent years, in addition to CD-DA (CD-Digital Audio), which is arecording medium for reproduction only, CD-R (CD-Recordable), whichallows recording digital data only one time, and CD-RW (CD-ReWritable),which allows rewriting digital data a multiple of times, have also cometo be used.

[0005] When recording data onto or when reproducing data from an opticaldisc, it is necessary to rotate the optical disc at a specific rpm, andin the case of a recording medium for reproduction only, it is possibleto obtain the specified rpm by synchronizing the rpm with thereproduction frequency of the digital data. On the other hand, in thecase of a recordable recording medium such as CD-R or CD-RW, there areno digital data initially recorded on the tracks and it is not possibleto control the rpm using the same method. Therefore, in the case of arecordable recording medium, the track (group track) that corresponds tothe address data wobbles, and the rpm is controlled based on a wobblesignal that is read from that track and the address of the track isidentified.

[0006] Currently, a method of recording an FM modulated wobble signal onthe track is known as a method for recording address data that useswobbling. Also, a method of recording address data on a track by phasemodulation of the wobble signal is disclosed in Japanese Laid-openpatent application No. H10-69646.

[0007] However, there is a demand to further increase the recordingdensity of an optical disc. In order to increase the recording densityof an optical disc, it is necessary to reduce as much as possible thespacing between spiral shaped tracks (spacing in the radial direction ofthe optical disc), however reducing the spot diameter of the laser beamsuch that it fits completely in the area formed by the track becomesdifficult, and a problem exists in that cross-talk from an adjacenttracks occurs.

[0008]FIGS. 22A to 22D are figures showing the effect of cross-talk froman adjacent track on the wobble signal. FIG. 22A shows the case when thewobble of the adjacent tracks has the same phase, FIG. 22B shows thecase when the wobble of the adjacent tracks has the reverse phase, FIG.22C show the case when the wobble of the adjacent tracks lags by 90degrees, and FIG. 22D shows the case when the wobble of the adjacenttracks leads by 90 degrees. FIGS. 22A to 22D, show the effect of theadjacent tracks (track n and track n+2) on the wobble signal for acenter track that is indicated as track n+1.

[0009] Also, there is a problem in that jitter in the recording clockthat is generated by a PLL (phase locked loop) from the wobble increasesdue to the effect of this kind of cross-talk. The wobble signal is notonly used for controlling the disc rotation, but is also used forgenerating a clock (recording clock) by way of the PLL that becomes atime reference when recording data onto the disk. Therefore, as shown inFIG. 22C or FIG. 22D, for example, when the wobble signal fluctuates inthe time-axis direction due to the effect of cross-talk, there is achance that it will cause jitter in the recording clock.

[0010] A method has also been proposed of canceling out cross-talk fromthe wobble signal. This method detects the cross-talk based on thecorrelation between the wobble signal from the track being reproducedand the tracks adjacent to that track. In this case, in order to be ableto detect the cross-talk, the correlation between the wobble signals iscontrolled such that it is a minimum. Addresses are normally assignedserial numbers that increase in order incrementally, which gives astrong correlation between addresses of adjacent tracks. Therefore,naturally a strong correlation occurs between the wobble signals oftracks that are modulated and recorded based on the address data. Inthis method, when there is a strong correlation between addresses, it isnot possible to detect the cross-talk accurately. Therefore, it is notpossible to reproduce the address data accurately.

[0011] In order to solve the problems described above, the object of thepresent invention is to provide a data recording method and opticrecording medium that is capable of reproducing address data accuratelyby reducing the correlation of address data between adjacent tracks,reducing the effect of cross-talk between adjacent tracks on therecording clock and by making it possible to apply a cross-talkcanceller to the wobble signal.

SUMMARY OF THE INVENTION

[0012] The above object of the present invention can be achieved by adata-recording method of the present invention. The data-recordingmethod of recording data while controlling the correlation between afirst data string and a second data string that are contained in therecording data, and is provided with a selecting process of selectinginversion/no inversion of the first data string such that thecorrelation between the first data string and the second data string isreduced; and a recording process of recording the first data stringaccording to the selected inversion/no inversion polarity, and recordingcontrol code that indicates whether inversion/no inversion was selectedfor the first data string.

[0013] According to the present invention, recording is performed byselecting inversion/no inversion for a first data string that willreduce the correlation between a first data string and a second datastring such that it is possible to reduce the correlation between thefirst data string and second data string. Also, a control code thatindicates whether inversion/no inversion is selected for the first datastring is recorded, so it is possible to accurately restore the firstdata string.

[0014] In one aspect of the present invention can be achieved by thedata-recording method of the present invention. The present inventionwherein: the recording data are recorded in order on tracks of adisc-shaped recording medium, and the first data string and second datastring are recorded on adjacent tracks.

[0015] According to the present invention, correlation between the firstdata string and second data string that are recorded on adjacent tracksis reduced, so it is possible to obtain an accurate tracking signal.

[0016] In another aspect of the present invention can be achieved by thedata-recording method of the present invention. The data-recordingmethod, wherein: the control code is contained in the first data string,and the selection procedure of selecting inversion/no inversion for thefirst data string selects whether to invert or not invert the first datastring such that the correlation between the first data string, whichcontains the control code, and the second data string is reduced.

[0017] According to the present invention, correlation with the finalrecording data that contains the control code and first data string isreduced, so selecting inversion/no inversion for the first data stringis executed under optimum conditions.

[0018] In further aspect of the present invention can be achieved by thedata-recording method of the present invention. The data-recordingmethod is further provided with an adding process of adding the controlcode to the start of the first data string according to whetherinversion or no inversion is selected; and a performing process ofperforming NRZI conversion of the data generated by the adding processof adding the control code; and wherein the recording process ofrecording the first data string and the control code, records the dataafter the NRZI conversion.

[0019] According to the present invention, by performing NRZI conversionfor just the first data string to which a specified control code isadded to the start, it is possible to control inversion/no inversion ofthe first data string during recording according to the control code.

[0020] In further aspect of the present invention can be achieved by thedata-recording method of the present invention. The data-recordingmethod, wherein: the first data string and the second data string areaddress data for the recording medium on which the first string and thesecond data string are recorded.

[0021] According to the present invention, it is possible to read theaddress data accurately.

[0022] The above object of the present invention can be achieved by adata-recording method of the present invention. The data-recordingmethod of scrambling and recording address data onto a recording mediumand comprising: a generating process of generating scramble key databased on the address data; a selecting process of selecting differentscrambling methods based on the key data and scrambling the addressdata; and a recording process of recording the key data and thescrambled address data on the recording medium.

[0023] According to the present invention, address data are scrambled byselecting a plurality of different scramble methods based on the keydata, and then the key data and scrambled address data are recorded onthe recording medium, so for example, by using different scramblemethods for adjacent tracks, it is possible to reduced the correlationof the address data between adjacent tracks and thus suppress the effectof cross-talk on address data for the wobble signals. Therefore, forexample, in addition to being able to reduce jitter in the recordingclock, it is possible to accurately reproduce the address data.

[0024] In one aspect of the present invention can be achieved by thedata-recording method of the present invention. The data-recordingmethod, wherein: the scrambling process scrambles only the higher-orderdata of the address data and does not scramble the lower-order data ofthe address data; and wherein the lower-order data are used as the keydata.

[0025] According to the present invention, only the higher-order addressdata, which have the largest effect on the correlation between datastrings contained in the address data, are scrambled, so it is possibleefficiently reduce the correlation between data strings. Also, thelower-order address data that do not have a large effect on thecorrelation between data strings can be effectively used as key data torestore the higher-order data.

[0026] In another aspect of the present invention can be achieved by thedata-recording method of the present invention. The data-recordingmethod is further provided with an interleaving process of interleavingthe higher-order data of the scrambled address data and lower-order dataof the address data that is used as the key data; a modulating processof modulating the data generated by interleaving and; a recordingprocess of recording the after interleaving data on the recordingmedium.

[0027] According to the present invention, it is possible to reduce thecorrelation between lower-order address data as well, and thus it ispossible to further reduce the correlation between the overall addressdata.

[0028] In further aspect of the present invention can be achieved by thedata-recording method of the present invention. The data-recordingmethod is, wherein the modulating process of modulating data executesNRZI conversion.

[0029] According to the present invention, the value of the lower-orderaddress data changes according to the values of the data surrounding thelower-order address data, so it is possible to effectively reduce thecorrelation of the lower-order data.

[0030] In further aspect of the present invention can be achieved by thedata-recording method of the present invention. The data-recordingmethod is, wherein the modulating process of modulating data executesNRZ conversion.

[0031] According to the present invention, the value of the lower-orderaddress data changes according to the values of the data surrounding thelower-order address data, so it is possible to effectively reduce thecorrelation of the lower-order data.

[0032] The above object of the present invention can be achieved by adata-recording medium of the present invention. The data-recordingmedium on which recording data are recorded while the correlationbetween a first data string and a second data string that are containedin the recording data is controlled, is provided with inversion/noinversion of the first data string is selected such that the correlationbetween the first data string and the second data string is reduced; andthe first data string is recorded according to the selected inversion/noinversion polarity, and control code that indicates inversion/noinversion is selected for the first data string.

[0033] In one aspect of the present invention can be achieved by thedata-recording medium of the present invention. The data-recordingmedium is, wherein: the control code is contained in the first datastring, and inversion/no inversion for the first data string is selectedsuch that the correlation between the first data string, which containsthe control code, and the second data string is reduced.

[0034] According to the present invention, correlation with the finalrecording data that contains the control code and first data string isreduced, so selecting inversion/no inversion for the first data stringis executed under optimum conditions.

[0035] In another aspect of the present invention can be achieved by thedata-recording medium of the present invention. The data-recordingmedium is, wherein: the control code is added to the start of the firstdata string according to whether inversion or no inversion is selected;and NRZI conversion is performed on the data generated by a procedure ofadding the control code; and when recording the first data string andthe control code, the data is recorded after the NRZI conversion.

[0036] According to the present invention, NRZI conversion is performedon just the first data string to which a specified control code is addedto the start, so it is possible to control inversion/no inversion of thefirst data string during recording according to the control code.

[0037] In further aspect of the present invention can be achieved by thedata-recording medium of the present invention. The data-recordingmedium is, wherein: the first data string and the second data string areaddress data on the recording medium on which the first string and thesecond data string are recorded.

[0038] According to the present invention, it is possible to read theaddress data accurately.

[0039] In further aspect of the present invention can be achieved by thedata-recording medium of the present invention. The data-recordingmedium is provided with address data for the data-recording medium arescrambled and the scrambled address data are recorded on thedata-recording medium, and when performing the scrambling, onlyhigh-order data of the address data are scrambled.

[0040] According to the present invention, the higher-order address datathat have a large effect on the correlation between data strings thatcontain the address data are scrambled, so it is possible to efficientlyreduce the correlation between data strings.

[0041] In further aspect of the present invention can be achieved by thedata-recording medium of the present invention. The data-recordingmedium is, wherein: lower-order data of the address data that are notscrambled are recorded on the data-recording medium as the scramble keydata for the higher-order data.

[0042] According to the present invention, correlation between datastrings that contain address data are effectively reduced and it ispossible to restore the higher-order data by using the lower-order dataas key data.

[0043] In further aspect of the present invention can be achieved by thedata-recording medium of the present invention. The data-recordingmedium is, wherein: the higher-order data of the scrambled address dataand lower-order data of the address data that is used as the key dataare interleaved; the data generated by interleaving are modulated; andthe modulated data are recorded on the data-recording medium.

[0044] According to the present invention, it is possible to reduce thecorrelation of lower-order address data, so it is possible to furtherreduce the correlation of the overall address data.

[0045] In further aspect of the present invention can be achieved by thedata-recording medium of the present invention. The data-recordingmedium is, wherein: NRZI conversion is executed when modulating thedata.

[0046] According to the present invention, the value of the lower-orderaddress data changes according to the value of the data surrounding thelower-order address data, so it is possible to effectively reduce thecorrelation of the lower-order address data.

[0047] In further aspect of the present invention can be achieved by thedata-recording medium of the present invention. The data-recordingmedium is, wherein: NRZ conversion is executed when modulating the data.

[0048] According to the present invention, the value of the lower-orderaddress data changes according to the value of the data surrounding thelower-order address data, so it is possible to effectively reduce thecorrelation of the lower-order address data.

[0049] According to the present invention, the address data on therecording medium are scrambled so it is possible to reduce thecorrelation of the address data. Also, scramble key data are generatedand recorded based on the original address data before scrambling, so itis possible to restore the scrambled address data.

BRIEF DESCRIPTION OF THE DRAWINGS

[0050]FIG. 1 is a drawing showing a first embodiment of thedata-recording method of the invention.

[0051]FIG. 2 is a drawing showing a different form of the firstembodiment of the data-recording method of the invention.

[0052]FIG. 3A and FIG. 3B are concept drawings of an Maximum-lengthsequences generation method, where FIG. 3A shows an initial-valueswitching method, and FIG. 3B shows a feedback switching method.

[0053]FIG. 4 is a block diagram showing the configuration of a scramblecircuit that corresponds to the initial-value switching method.

[0054]FIG. 5 is a block diagram showing the configuration of a scramblecircuit that corresponds to the feedback switching method.

[0055]FIG. 6 is a drawing showing a second embodiment of thedata-recording method of the invention.

[0056]FIG. 7A and FIG. 7B are drawings showing an interleaving method,where FIG. 7A shows the entire method and FIG. 7B shows part of themethod.

[0057]FIG. 8A, FIG. 8B and FIG. 8C are drawings showing the logiccircuits for conversion, where FIG. 8A is a drawing of a logic circuitfor NRZI conversion, FIG. 8B is a drawing of a logic circuit for NRZconversion and FIG. 8C is a drawing showing a truth-value table for thecircuits shown in FIG. 8A and FIG. 8B.

[0058]FIG. 9 is a time chart of the input/output data in NRZIconversion.

[0059]FIG. 10 is a drawing showing the process of recording address datain a third embodiment of the invention.

[0060]FIG. 11A and FIG. 11B are drawings showing an example of insertingcontrol code between address data, where FIG. 11A shows the originaladdress data, and FIG. 11B shows the state after control code has beeninserted.

[0061]FIG. 12 is a drawing showing an example of the procedure forcontrolling the correlation control.

[0062]FIG. 13A and FIG. 13B are drawings showing the effect ofcorrelation control, where FIG. 13A shows the case when correlationcontrol is not executed, and FIG. 13 shows the case when correlationcontrol is executed.

[0063]FIG. 14 is a drawing showing the recording procedure.

[0064]FIG. 15 is a drawing showing the procedure when adding controlcode to encoded data.

[0065]FIG. 16 is a flowchart showing the procedure of selecting controlcode.

[0066]FIG. 17 is a drawing showing the method of selecting control code.

[0067]FIG. 18A and FIG. 18B are drawings showing the sum of the datacorrelation after 1-bit to 2-bit conversion (encoding) of two randomseries (Maximum-length sequences), where FIG. 18A shows the case whencoefficient control is not performed, and FIG. 18B shows the case whencoefficient control is executed.

[0068]FIG. 19 is a drawing showing three adjacent tracks.

[0069]FIG. 20 is a drawing showing the configuration of tracks on anoptical disc that is used as the recording medium to which thedata-recording method of the invention is applied.

[0070]FIG. 21 is a drawing showing the spiral-shaped tracks expandedinto a straight linear shape.

[0071]FIG. 22A, FIG. 22B, FIG. 22C and FIG. 22D are drawings showing theeffect of cross-talk from adjacent tracks on the wobble signal, whereFIG. 22A shows the case when the wobble of the adjacent tracks have thesame phase, FIG. 22B shows the case when the wobble of the adjacenttracks have the reverse phase, FIG. 22C shows the case when the wobbleof the adjacent tracks lag by 90 degrees, and FIG. 22D shows the casewhen the wobble of the adjacent tracks lead by 90 degrees.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0072] A first embodiment of the data-recording method of the inventionwill be explained with reference to FIG. 1 to FIG. 5.

[0073] -First Embodiment-

[0074] In the first embodiment of the data-recording method, thehigher-order byte of the address data is scrambled and recorded, and thelower-order byte is recorded without being scrambled. The lower-orderbyte that is recorded without being scrambled is used as the scramblekey data.

[0075]FIG. 1 is a drawing showing the first embodiment of thedata-recording method of the invention. As shown in FIG. 1, the IDcomprises four bytes of address data, and two bytes of parity data. Theaddress data before scrambling comprises four bytes of data, A3, A2, A1and A0. Also, the parity comprises two bytes of data, P1 and P0.

[0076] In this first embodiment, the lowest-order data A0 of the addressdata stays as is, and the other higher-order data, A3 to A1 arescrambled. Data A0 is used as the scramble key data.

[0077] As shown in FIG. 1, random data M3, M2 and M1, which differ fromeach other, are generated based on the lowest-order data A0 that iscontained in the address data. Also, data B3 are generated by taking theexclusive OR of data A3 and random data M3, data B2 are generated bytaking the exclusive OR of data A2 and random data M2, and data B1 aregenerated by taking the exclusive OR of data A1 and random data M1.

[0078] By applying the 2-byte parity to the scrambled data B3 to B1 andthe non-scrambled data A0, random parity is generated from the two bytesof data P1 and P0 since data B3 to B1 are randomized.

[0079] Instead of applying parity to the scrambled address data, it ispossible to scramble the data P1 and P0 that are added to the addressdata before scrambling to obtain data P1 a and P0 a.

[0080] Since the higher-order bytes of the address data do not changefrequently, strong correlation occurs between adjacent tracks when thosedata are recorded as they are. However, in this first embodiment, thehigher-order data A3 to A1 are scrambled and then recorded, so it ispossible to greatly reduce the correlation between adjacent tracks.

[0081] On the other hand, since the lower-order bytes of address datachange frequently, strong correlation does not occur between adjacenttracks for data A0. Therefore, there is no chance of strong correlationoccurring between adjacent tracks even though the lower-order data A0 ofthe address data are recorded as scramble key data without beingscrambled.

[0082] In this first embodiment, it is possible to randomize thehigher-order bytes that create a strong correlation in this way, and byusing the lower-order byte that does not create strong correlation asthe scramble key data, it becomes possible to descramble the addressdata during reproduction.

[0083] It is also possible to record the scrambled signal as is, forexample, it is possible to modulate the signal using a method such asphase-shift keying and then record the signal.

[0084]FIG. 2 is a drawing showing an example of a different form of thefirst embodiment of the data-recording method of the invention. In theexample shown in FIG. 2, the lower-order byte of address data does notremain as is to be used as key data, but rather the scramble key dataare generated based on the address data, and those key data are added tothe ID.

[0085] As shown in FIG. 2, in this example, key data are generated basedon the address data A3 to A0, and then random data M3 to M0 aregenerated based on the key data. Also, data B3 are generated by takingthe exclusive OR of address data A3 and random data M3, data B2 aregenerated by taking the exclusive OR of address data A2 and random dataM2, data B1 are generated by taking the exclusive OR of address data A1and random data M1, and data B0 are generated by taking the exclusive ORof address data A0 and random data M0.

[0086] The 2-byte parity data P1 and P0 can be added to the scrambleddata B3 to B0, or by scrambling data P1 and P0 that are added to theaddress data before scrambling, data P1 a and P0 a can be generated.

[0087] By thinking of the lower-order byte of the address data as keydata, the configuration shown in FIG. 1 can be interpreted as a specialcase of the configuration shown in FIG. 2.

[0088] It is possible to use a typical Maximum-length sequencesgeneration circuit as the method of generating the random data shown inFIG. 1 and FIG. 2. FIG. 3A and FIG. 3B are concept drawings showing theMaximum-length sequences generation method, where FIG. 3A shows aninitial-value switching method, and FIG. 3B shows a feedback switchingmethod. Also, FIG. 4 is a block diagram showing the configuration of ascramble circuit that corresponds to the initial-value switching method,and FIG. 5 is a block diagram showing the configuration of a scramblecircuit that corresponds to the feedback switching method.

[0089] As shown in FIG. 3A, in the initial-value switching method,initial values are generated based on the lower-order byte of theaddress data or based on the scramble key data.

[0090] The scramble circuit shown in FIG. 4 comprises an initial-valuegeneration circuit 201, an Maximum-length sequences generation circuit202 comprising a shift register 203 and EXOR circuit 204, and an EXORcircuit 205. The Maximum-length sequences generation circuit 202 shownin FIG. 4 is an example of configuration using a 15-stage (R0 to R14)shift register 203, and together with shifting the bits from each stagein order in the shift direction, the EXOR circuit 204 takes theexclusive OR of the bits output from specified stages (R10 and R14 inFIG. 4) of the shift register 203 and feeds the result back to theinitial stage R0. The Maximum-length sequences generation circuit 202generates an Maximum-length sequences of random data having a 2^ 15-1(bits) cycle.

[0091] On the other hand, the initial-value generation circuit 201prepares in advance a plurality of partial series that appear in theMaximum-length sequences cycle as initial values based on the recordingposition data for the disc, and from among these values sets initialvalues that are selected based on the lower-order byte of the addressdata or on the key data, and sets them for the Maximum-length sequencesgeneration circuit 202. More specifically, it is possible to prepare atable for conversion between the lower-order byte of the address data orkey data and the initial values. It is also possible to use the initialvalues as they are as the key data shown in FIG. 2.

[0092] Since construction is such that the initial values are switchedin this way by the initial-value generation circuit 201, it is possibleto perform different scrambling according to the recording position.Also, by taking the exclusive OR of the output bit from a specifiedstage (R7 in FIG. 4) of the shift register 203 and the address data inthe EXOR circuit 205, the address data are scrambled and output from thecircuit as scrambled data.

[0093] As shown in FIG. 3B, in the feedback switching method, thefeedback circuit is switched based on the lower-order byte of theaddress data or the scramble key data.

[0094] The Maximum-length sequences generation circuit 21 shown in FIG.5 comprises a 14-stage shift register 101, feedback bit selector 102 andEXOR circuits 103 a to 103 c. Here, through the function of the feedbackbit selector 102 as a way of switching the feedback of theMaximum-length sequences generation circuit 21, the connection to theoutput bits from each stage of the shift register 101 is switched and itis possible to selectively set a plurality of primitive polynomials.

[0095] In FIG. 5, the shift register 101 has fourteen stages representedby R0 to R13, and shifts sequential data in the shift directionindicated by the arrow (direction from R0 to R13), then outputs outputbits (x0 to x13) from each stage based on the specified primitivepolynomials. The thirteen output bits are entered into the feedback bitselector 102 which then sets a connection relationship that correspondsto the setting data of the primitive polynomials that were selectedbased on the lower-order address data or key data, and outputs threeselected bits s1, s2 and s3. More specifically, it is possible toprepare a conversion table for conversion between the lower-order byteof the address data or key data and the feedback bit position. For thecase shown in FIG. 2, it is also possible to use the feedback bitposition itself as key data.

[0096] Also, the EXOR circuit 103 a takes the exclusive OR of the0th-degree output bit (x0) from R13 of the shift register 101 and theselected bit s1. The EXOR circuit 103 b takes the exclusive OR of theoutput bit from the EXOR circuit 103 a and the selected bit s2. The EXORcircuit 103 c takes the exclusive OR of the output bit from the EXORcircuit 103 b and the selected bit s3. Finally, the output bit (x14)from the EXOR circuit 103 c is fed back to the first stage RO of theshift register 101.

[0097] The EXOR circuit 105 scrambles the address data by taking theexclusive OR of the output bit from a specified stage (R7 in FIG. 5) ofthe shift register 101 and the address data, and outputs the data asscrambled data.

[0098] -Second Embodiment-

[0099] A second embodiment of the data-recording method of the inventionwill be explained with reference to FIG. 6 to FIG. 9.

[0100] Similar to the data-recording method of the first embodiment, inthe data-recording method of this second embodiment, the higher-orderbytes of the address data are scrambled and the lower-order byte is notscrambled. However, in this second embodiment, the correlation betweenadjacent tracks is further reduced by performing interleaving of thescrambled higher-order bytes and non-scrambled lower-order byte.

[0101]FIG. 6 is a drawing showing the second embodiment of thedata-recording method of the invention.

[0102] Similar to the first embodiment, in this second embodiment,random data M3, M2 and M1, which differ from each other, are generatedbased on the lowest-order data A0 contained in the address data. Also,data B3 are generated by taking the exclusive OR of address data A3 andrandom data M3, data B2 are generated by taking the exclusive OR ofaddress data A2 and random data M2, and data B1 are generated by takingthe exclusive OR of address data A1 and random data M1. The existence ofparity is arbitrary.

[0103] Next, interleaving is performed on data B3 to B1 and data A0.FIG. 7A and FIG. 7B are drawings showing the interleaving method, whereFIG. 7A shows the entire method and FIG. 7B shows a part of the method.

[0104] As shown in FIG. 7A and FIG. 7B, the bits of the lower-order byteof data A0 of the remaining address data that are used as key data arerewritten (interleaved) with the positions of bit 4 and bit 0 of data B3to B1 and data A0. The data corresponding to the positions of bit 4 andbit 0 of each byte are rewritten as the positions of specified bits ofdata A0. As shown in FIG. 6, by interleaving, data B3 to B1 and A0 areconverted to data C3 to C0. With this kind of interleaving, each of thenon-scrambled bits, or in other words, each of the bits of the data A0,which cause correlation to occur, are located between each bit of therandomized higher-order bytes.

[0105] Next data C3 to C0 are modulated depending on 1/0 state of thefront/rear bits such that the modulated data differ. In this way, themodulated data of each bit of data A0 are randomized by the randomnessof the front/rear bits. Therefore, it is possible to do away with theeffect on correlation by data A0.

[0106] For example, NRZI conversion is conversion where the output isinverted when the data is 1 and the output is not inverted when the datais 0, and the conversion results are different depending on whether thepreviously converted bit is 1 or 0 even when the data are the same.Regardless of whether or not NRZI conversion is performed, it ispossible to take the exclusive OR with the previous bit.

[0107]FIG. 8A, FIG. 8B and FIG. 8C are drawings showing the logiccircuit for conversion, where FIG. 8A shows a logic circuit for NRZIconversion and FIG. 8B shows a logic circuit for NRZ conversion. FIG. 8Cis a drawing showing a truth-value table for the circuits shown in FIG.8A and FIG. 8B. FIG. 9 is a time chart for the input/output data in NRZIconversion. FIG. 9 shows the case of converting the bit sequence of dataC3, and shows the case when A0(7)=A0(6)=0.

[0108] As shown in FIG. 8A to FIG. 8C, in NRZI and NRZ conversion, whenthe previous bit (previous one bit of output or input) is zero, theoutput bit becomes the same as the input bit. When the previous bit is1, the output bit is inverted with respect to the input bit.

[0109] For example, when the bit of C3(5) in FIG. 9 changes, the bit ofA0(7), which was rewritten in the position of C3(4), changes from 0to 1. Also, in connection with this change, the bit of A0(6), which wasrewritten in the position of C3(0), changes from 1 to 0. By changing thesurrounding bits in this way, the values (0/1) immediately afterconversion change even when the data are the same. Therefore, data A0 israndomized through this kind of conversion.

[0110] It is also possible to record the scrambled signal as is. Forexample, it is possible to modulate the signal using a method such asphase-shift keying, and then record the signal.

[0111] -Third Embodiment-

[0112] A third embodiment of the data-recording method of the inventionwill be explained with reference to FIG. 10 to FIG. 19.

[0113] In the following explanation, the correlation between two datastrings is defined as “(Number of matching bits)−(Number of non-matchingbits)”. This definition is different than the normal definition ofcorrelation, however, in order to simplify the explanation, thisdefinition will be used here. For example, in the case of correlationbetween two identical data strings, all of the bits match, so itconsidered to be very positive correlation. When (Number of matchingbits)=(Number of non-matching bits), the correlation is zero and thereis no correlation between the data strings. In the case when none of thebits match, the data string is completely inverted and there is largenegative correlation.

[0114] By inverting one of the two data strings, bits are changed suchthat bits that matched become non-matching bits, and bits that did notmatch become matching bits. So using the definition described above, itis possible to invert the polarity of the correlation between the datastrings.

[0115]FIG. 10 is a drawing showing the process of recording address datain this third embodiment of the invention. As shown in FIG. 1, parity isadded after scrambling the generated address data. By further encodingthe data and comparing it with the data of the previous track,correlation control is executed to invert data in order to lower thecorrelation. Details about this correlation control will be describedlater. It is possible to record the data, for which correlation controlwas executed, as are. For example, it is possible to modulate the datausing a method such as phase-shift keying, and then record the data.

[0116] As shown in FIG. 10, generating the address data, scrambling thedata, adding parity and encoding the data can be executed by an addressencoder 11. The order of performing encoding and correlation control canbe switched.

[0117] Adding the parity as shown in FIG. 10 is adding code (parity) fordetecting errors or for correcting errors.

[0118] Next, the correlation control will be explained. By controllinginversion/no inversion of the recording data, it is possible to controlthe polarity of the correlation. Therefore, it is possible to reducecorrelation by properly selecting inversion/no inversion. However, byjust inverting recording data, it is impossible to return to theoriginal data (decode the data), so in addition to the recording data(ID), it is necessary to add control code that indicates whether therecording data have been inverted or not inverted.

[0119]FIG. 11A and FIG. 11B are drawings showing an example of insertingcontrol code between address data. FIG. 11A shows the original addressdata and FIG. 11B shows the state after the control code has beeninserted.

[0120]FIG. 12 shows an example of the correlation control procedure. Inthis example, the characteristics of NRZI conversion are used. In thecase of recording after NRZI conversion, when ‘1’ is inserted in theinput data string, the recording data after it are inverted, and when‘0’ is inserted in the input data string, the recording data after itare not inverted. In using these characteristics, by inserting one bitof data at a certain interval in the input data string ascorrelation-control code, it is possible to control inversion/noinversion of the output data string (recording data). In other words, toinvert recording data for a certain section, ‘1’ is used as control code(control code added at the beginning of that section) to indicate noinversion/inversion for that section. Also, to not invert recording datafor a certain section, ‘0’ is used as control code (control code addedat the beginning of that section) to indicate no inversion/inversion forthat section.

[0121] By reading the control code during reproduction, it is possibleto determine whether or not the data corresponding to that control codehas been inverted and recorded, so it possible to properly decode databefore NRZI conversion.

[0122] When determining whether or not to invert recording data for aspecified section, in both the case to invert and record and the case torecord without inverting, it is possible to calculate and determine thecorrelation with the data recorded on the previous track. In otherwords, in both the case when the control code is ‘0’ (no inversion) andNRZI conversion is performed and the data are recorded, and the casewhen the control code is ‘1’ (inversion) and NRZI conversion isperformed and the data are recorded, the correlation between the data upuntil just before the next control code and the data that are recordedon the track before those data is calculated, and the control code thatgives the smaller absolute value of correlation is selected as thecontrol code and is inserted into the input data string. An example ofthe algorithm used for selecting the control code will be describedlater.

[0123]FIG. 13A and FIG. 13B are drawings showing the effect ofcorrelation control, where FIG. 13A shows the case when correlationcontrol is not executed, and FIG. 13B shows the case when correlationcontrol is executed. In FIG. 13A, the correlation for each section istotaled, and the absolute value of the sum of the correlation increases.On the other hand, in FIG. 13B, by continuing to select control codesuch that the sum of the correlation becomes smaller, the absolute valueof the sum of the correlation does not increase.

[0124] A method of using the NRZI conversion characteristics wasexplained as an example of correlation control, however, any kind ofcontrol code can be inserted as long as, 1) it is possible to controlinversion/no inversion of recording data, and 2) it is possible torestore the original data even though the recording data have beeninverted.

[0125] For example, together with simply inverting or not inverting thedata for each specified section, it is possible to insert a bit ascontrol code indicating whether inversion or no inversion has beenperformed for each section. By taking ‘1’ to be control code indicatinginversion, and ‘0’ to be control code indicating no inversion, when thecontrol code read during decoding is ‘1’, it is possible to properlydecode the data by inverting the data for that specified section.

[0126] As another example, there is a method of performing modulationand NRZI conversion by using RLL code to convert 1-bit data to 2-bitdata. For example, by performing conversion such that when the originaldata is ‘0’, the converted data becomes ‘10’, and when the original datais ‘1’, the converted data becomes ‘11’, only 1T and 2T are output andthe DC component is lost.

[0127]FIG. 14 shows the recording procedure in this case. As shown inFIG. 14, encoding by 1-bit to 2-bit conversion is executed afterinserting control code into the ID data string. Next, NRZI conversion isperformed and the data are recorded. When original data ‘0’ is insertedas control data, it is converted to ‘10’ by encoding. In this case,through NRZI conversion, Inversion+No inversion=Inversion. When theoriginal data ‘1’ is inserted as control code, it is converted to ‘11’by encoding. In this case, through NRZI conversion,Inversion+Inversion=No inversion. Therefore, by inserting control codeinto the data before encoding, it is possible to control inversion/noinversion.

[0128] Inserting the control code 10/11 into the data after encodinginstead of inserting control code 0/1 into the data before encoding, hascompletely the same effect. FIG. 15 shows the procedure in the case ofadding control code to the data after encoding. In this case, as shownin FIG. 15, the control code 10/11 is inserted into the data after theID code has been encoded. Next, NRZI conversion is performed and thedata are recorded.

[0129] The methods described above are examples, and it is possible toarbitrarily select a method for inverting or not inverting the recordingdata. The data-recording method of this invention is not limited by thetype of control code used, or the stage when the control code isinserted. Also, the invention is not limited by whether or not the dataare recorded using NRZI conversion, or whether or not encoding isperformed for the recording data.

[0130] Next, FIG. 16 and FIG. 17 will be used to explain the algorithmfor selecting the control code. FIG. 16 is a flowchart showing theprocedure of selecting the control code, and FIG. 17 is a drawingshowing the method of selecting the control code.

[0131] In step S1 in FIG. 16, the value of the correlation sum is resetto zero. Next, in step S2, assuming that the control code for noinversion has been selected, the correlation C1 for the section up tothe next control code is calculated. Next, in step S3, assuming that thecontrol code for inversion has been selected, the correlation C2 for thesection up to the next control code is calculated.

[0132] As shown in FIG. 17, in step S2 and step S3, correlation betweenthe data of the section starting from the control code, for whichinversion/no inversion is to be determined, up to the start of the nextcontrol code, and the data of the previous track, is calculated. Thecorrelation sum is the total of the correlation up to the start of thecontrol code for which inversion/no inversion is to be determined.

[0133] Next, in step S4, the absolute value of the correlation sum towhich C1 has been added and the absolute value of the correlation sum towhich C2 has been added are compared to determine which is larger orsmaller, and when it is determined that the latter value is larger, thenthe process advances to step S5, however, when it is determined that theformer value is larger, then the process advances to step S7.

[0134] In step S5, the control code is set for no inversion. Next, instep S6, the correlation C1 is added to the sum and the process advancesto step S9.

[0135] On the other hand, in step S7, the control code is set forinversion. Next, in step 8, the correlation C2 is added to the sum andthe process advances to step S9.

[0136] In step S9, the control code for which inversion/no inversion isto be determined is switched to the next code and the process returns tostep S2. By repeating the processing of step S2 to step S9, the controlcodes for each section are selected in order.

[0137]FIG. 18A and FIG. 18B are drawings showing the calculated sum ofthe correlation between two random series (Maximum-length sequences)after 1-bit to 2-bit conversion (encoding), where FIG. 18A shows thecase when correlation control is not executed, and FIG. 18B shows thecase when correlation control is executed. In FIG. 18B, after every twobytes (16 bits) 1-bit control code is inserted and then encoding isperformed.

[0138] As shown in FIG. 18A, when control code is not inserted, thecalculated sum of the correlation increases as the number of bitsincreases. That is, a certain amount of correlation occurs even whenscrambling is performed using random series (Maximum-length sequences).

[0139] On the other hand, as shown in FIG. 18B, when control code isinserted, the calculated sum of the correlation does not increase as thenumber of bits increases. Therefore, it can be seen that by executingcorrelation control by inserting control code in this way, it ispossible to effectively reduce the correlation.

[0140] Next, correlation between three adjacent tracks will beexplained. FIG. 19 is a drawing showing the correlation between threeadjacent tracks.

[0141] In the correlation control described above, when recording thesecond track shown in FIG. 19, the control code for the recording dataon the second track is controlled such that the correlation between thedata recorded on the first track, which corresponds to the previoustrack, and the data to be recorded on the second track is a minimum.Therefore, the correlation between the first track and the second trackis reduced.

[0142] Moreover, when recording a third track, the control code for therecording data on the third track is controlled such that thecorrelation between the data recorded on the second track, whichcorresponds to the previous track, and the data to be recorded on thethird track is a minimum. Therefore, the correlation between the secondtrack and the third track is reduced.

[0143] In this way, the correlation between the recorded signal on thesecond track and the recorded signals on the adjacent first track andthird track is reduced. When the correlation between tracks is strong,it becomes difficult to extract the cross-talk component from the signalon the track being reproduced in order to cancel the cross-talk. Inother words, it becomes difficult to distinguish between the signalitself on the track being reproduced and the cross-talk component. Inthis regard, with the correlation control described above, thecorrelation between adjacent tracks is reduced so this is no problem.

[0144] However, in this method, the correlation between the first trackand the third track is not reduced. For example, when the signal on thefirst track is the same as the signal on the third track, it becomesdifficult to determine which cross-talk component can be extracted andwhich track the cross-talk is from. Therefore, it is preferred thatcorrelation be reduced by scrambling the signal of each track inadvance. In addition, by executing the correlation control describedabove, the correlation between the signal on the track being reproducedand both of the tracks adjacent to that track is reduced.

[0145] -Data-Recording Medium-

[0146]FIG. 20 is a drawing showing the track configuration on an opticaldisc 5 that is used as the data-recording medium to which thedata-recording method of the invention is applied. A track is formed onthe disc 5 in a spiral shape that runs from the inside to the outside.In FIG. 20, an example is shown in which track numbers (three tracks inFIG. 20, track n, track n+1 and track n+2) are assigned to eachrevolution starting from the inside.

[0147] It is possible to apply the data-recording method of thisinvention to the data that are recorded on the disc 5 shown in FIG. 20.In this case, it is possible to reduce the correlation between theaddress data on adjacent tracks as described above, and suppress theeffects of cross-talk. It is preferred that the scrambling method beswitched at intervals shorter than one revolution so that the samescrambling method is not used between adjacent tracks.

[0148]FIG. 21 is a drawing showing the spiral-shaped tracks shown inFIG. 20 expanded into a straight line, and shows eight addressesrecorded around one track. The numbers (0 to 31) in FIG. 21 indicate thelower-order data on each track. In the case of the disc shown in FIG.21, none of the lower-order data on the three adjacent tracks match.Therefore, as was shown in the embodiments described above, by selectinga different scrambling method corresponding to each respectivelower-order data, the correlation between adjacent tracks is reduced. Inthis way, the same scrambling method does not appear in the tracks forat least two revolutions, and by switching the scrambling method inorder, it is possible to reduce the correlation between adjacent tracks.

[0149] It is possible to record address data by performing phase-shiftmodulation (PSK modulation) or frequency modulation (FSK modulation) onthe wobble signal after randomizing the address data by scrambling andreducing the correlation between adjacent tracks in this way. In thiscase, it is not possible to remove the bad state of the S/N ratio itselfshown in FIG. 22A to FIG. 22D, however, since the states shown in FIG.22A to FIG. 22D appear alternately at short intervals, none of theindividual states continue for a long period of time. PLL does notfollow change that is faster than the control range (normally about 1kHz), so the generated recording clock operates in a state that ispractically the average of the states shown in FIG. 22A to FIG. 22D, orin other words in a state with no cross-talk. Therefore, it is possibleto reduce the effect of cross-talk on the recoding clock. Also, byreducing correlation of the data of adjacent tracks, it becomes possibleto detect the cross-talk properly, and by canceling the cross-talk, itbecomes possible to accurately reproduce the address data. Cancellationof the cross-talk referred to here is the reduction of the effects ofcross-talk from adjacent tracks by adding or subtracting the wobblesignals of adjacent tracks.

[0150] In the data-recoding method or data-recording medium of thisinvention, it is also possible to record the scrambled signals as are onthe data-recording medium. For example, it is possible to performmodulation, such as phase-shift modulation, on the scrambled signal, andthen record that modulated signal onto the data-recording medium.

[0151] The entire disclosure of Japanese Patent Application No.2001-275992 filed on Sep. 12, 2001 including the specification, claims,drawings and summary is incorporated herein by reference in itsentirety.

What is claimed is:
 1. A data-recording method of recording data whilecontrolling the correlation between a first data string and a seconddata string that are contained in said recording data, and comprising: aselecting process of selecting inversion/no inversion of said first datastring such that the correlation between said first data string and saidsecond data string is reduced; and a recording process of recording saidfirst data string according to said selected inversion/no inversionpolarity, and recording control code that indicates whether inversion/noinversion was selected for said first data string.
 2. The data-recordingmethod according to claim 1, wherein said recording data are recorded inorder on tracks of a disc-shaped recording medium, and said first datastring and second data string are recorded on adjacent tracks.
 3. Thedata-recording method according to claim 1, wherein said control code iscontained in said first data string, and said selection procedure ofselecting inversion/no inversion for said first data string selectswhether to invert or not invert said first data string such that thecorrelation between said first data string, which contains said controlcode, and said second data string is reduced.
 4. The data-recordingmethod according to claim 1, further comprising: an adding process ofadding said control code to the start of said first data stringaccording to whether inversion or no inversion is selected; and aperforming process of performing NRZI conversion of the data generatedby said adding process of adding said control code; and wherein saidrecording process of recording said first data string and said controlcode, records said data after said NRZI conversion.
 5. Thedata-recording method according to claim 1, wherein said first datastring and said second data string are address data for the recordingmedium on which said first string and said second data string arerecorded.
 6. A data-recording method of scrambling and recording addressdata onto a recording medium and comprising: a generating process ofgenerating scramble key data based on said address data; a selectingprocess of selecting different scrambling methods based on said key dataand scrambling said address data; and a recording process of recordingsaid key data and said scrambled address data on said recording medium.7. The data-recording method according to claim 6, wherein saidscrambling process scrambles only the higher-order data of said addressdata and does not scramble the lower-order data of said address data;and wherein said lower-order data are used as said key data.
 8. Thedata-recording method according to claim 7, further comprising: aninterleaving process of interleaving the higher-order data of saidscrambled address data and lower-order data of said address data that isused as said key data; a modulating process of modulating the datagenerated by interleaving; and a recording process of recording theafter interleaving data on said recording medium.
 9. The data-recordingmethod according to claim 8, wherein said modulating process ofmodulating data executes NRZI conversion.
 10. The data-recording methodaccording to claim 8, wherein said modulating process of modulating dataexecutes NRZ conversion.
 11. A data-recording medium on which recordingdata are recorded while the correlation between a first data string anda second data string that are contained in said recording data iscontrolled, comprising: inversion/no inversion of said first data stringis selected such that the correlation between said first data string andsaid second data string is reduced; and said first data string isrecorded according to said selected inversion/no inversion polarity, andcontrol code that indicates inversion/no inversion is selected for saidfirst data string.
 12. The data-recording medium according to claim 11,wherein said control code is contained in said first data string, andinversion/no inversion for said first data string is selected such thatthe correlation between said first data string, which contains saidcontrol code, and said second data string is reduced.
 13. Thedata-recording medium according to claim 11, wherein said control codeis added to the start of said first data string according to whetherinversion or no inversion is selected; and NRZI conversion is performedon the data generated by a procedure of adding said control code; andwhen recording said first data string and said control code, said datais recorded after said NRZI conversion.
 14. The data-recording mediumaccording to claim 11, wherein said first data string and said seconddata string are address data on said recording medium on which saidfirst string and said second data string are recorded.
 15. Adata-recording medium comprising: address data for said data-recordingmedium are scrambled and said scrambled address data are recorded onsaid data-recording medium, and when performing said scrambling, onlyhigh-order data of said address data are scrambled.
 16. Thedata-recording medium according to claim 15, wherein lower-order data ofsaid address data that are not scrambled are recorded on saiddata-recording medium as the scramble key data for said higher-orderdata.
 17. The data-recording medium according to claim 16, wherein thehigher-order data of said scrambled address data and lower-order data ofsaid address data that is used as said key data are interleaved; thedata generated by interleaving are modulated; and the modulated data arerecorded on said data-recording medium.
 18. The data-recording mediumaccording to claim 17, wherein NRZI conversion is executed whenmodulating said data.
 19. The data-recording medium according to claim17, wherein NRZ conversion is executed when modulating said data.
 20. Adata-recording medium comprising: address data on said data-recordingmedium are scrambled; scramble key data are generated based on originalsaid address data before scrambling; said scrambled address data arerecorded on said data-recording medium; and said generated key data arerecorded on said data-recording medium.
 21. The data-recording mediumaccording to claim 20, wherein said address data are scrambled bydifferent scramble methods between adjacent tracks and then recorded.